Concrete expansion and contraction joint

ABSTRACT

A concrete expansion and contraction joint is described incorporating an upper and lower section detachably engaged and including longitudinally extending water blocking anchors. The bottom wall of the upper section incorporates a V-shape having a contractual crack inducing edge; a pair of longitudinally extending channels are provided in the upper section beneath the water blocking anchors for receiving locking flanges positioned along the upper edges of the lower section. The flanges engage the channels to lock upper and lower sections into a unitary structure.

United States Patent Deason July 29, 1975 [54] CONCRETE EXPANSION AND 3,508,474 4/1970 Rowe 404/65 CONTRACTION JOINT 3,575,094 4/1971 Hewitt et al. 404/65 Max W. Deason, 5350 N. Estelle Dr., Tucson, Ariz. 85718 Filed: Apr. 4, 1974 Appl. No.: 457,964

Inventor:

US. Cl 52/396; 404/64 lnt. Cl. ..E01C 11/10 Field of Search 52/393, 396, 573, 403;

References Cited UNITED STATES PATENTS 6/1932 Adler 404/48 3/1962 Worson..... 6/1964 Dohren..... 4/1965 Crone 52/396 X Primary Examiner-Price C. Faw, Jr. Attorney, Agent, or Firm-*Cahill, Sutton & Thomas 57 5 ABSTRACT A concrete expansion and contraction joint is described incorporating an upper and lower section de-' 3 Claims, 2 Drawing Figures PATENTED JUL 2 9 I975 SHEET The present invention. pertains to concrete joint apparatus and more specif cally, to aconcrete joint to fa-.

cilitate the'pr'oper positioning of a contraction crack in aconcrete slab and for'accommodating, when desired,

the expansion of the concrete slab.

The expansion and contraction characteristics of concrete are well known; in those applications where conditions, may resultin raised and uneven slabs and even possible addi'tio'n'alcracking and unevenness.

To control such contraction cracks, a variety of joint configurations have been proposed in the prior art which will induce the slab to crack beneath the joint at a predetermined location with the joint covering the crack. In concrete slab environments such asswimming pools, it is frequently important not only to control contraction cracks, but also provide a means for accommodating slab expansion. To accommodate such expansion, the joint must extend the entire depth of the slab and be capable of withstanding the compressive forces exerted by the expanding concrete when the latter subsequently contracts.

It is therefore an object of the present invention to provide a concrete joint that may be utilized to accommodate contraction and expansion of a concrete slab.

It is another object of the present invention to provide a concrete joint that can be utilized to accommodate the contraction and ultimate cracking of a concrete slab while nevertheless optionally being capable of accommodating both the contraction and expansion of a concrete slab.

The present invention may be described with more clarity and specificity with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view, partly in section, of an expansion and contraction joint constructed in accordance with the teachings of the presentinvention with the upper and lower sections thereof separated; and

H6. 2 is a cross-sectional view of an expansion and contraction joint constructed in accordance with the teachings of the present invention with the upper and lower sections thereof in the engaged position.

Referring now to the drawings, an expansion and contraction joint is shown having an upper section 110 and a lower section 12. The upper section includes a top wall 14 and side walls 15 and 16. The bottom wall 18 of the upper section 10 is formed into a V-shape having a contractional crack inducing edge 20 extending longitudinally of the upper section. ltmay be noted that the bottom wall 18 also acts as a guide for the flanges of the bottom section (to be described hereinafter).

Longitudinally extending water blocking wings or anchors 22 and 24 are provided on either side of the upper section 10 and extend outwardly from side walls '15 and i6, repectively. These anchors 22 and 24 incorporate flanges 26 and 28 along the outside edges thereof which effectively lock the anchors into the concrete after it has solidified against either side of the joint. [longitudinally extending channels 30 and 32 are provided in each side of the upper section beneath the anchors 22 and 24. The channels 30 and 32 are adapted to receive locking flanges (to be described of the lower section 12.

The lowersection 12 includes side walls 34 and 36 and an inverted trough-shaped bottom 38. The top of the lower section is open while the upper edges of the side walls 34 and 36 are provided with longitudinally extending inwardly directed locking flanges 40 and 42. The flanges 40 and 42 engage the channels 30 and 32, respectively, of the upper section thereby locking the upper and lower sections into a unitary structure. A trough shaped internal web 44 extends between'walls 34 and 36 of the lower section while a trough shaped internal web 46 extends between the side walls 15 and 16 of the upper section.

The expansion and contraction joint of the present invention may be made from an extruded semi-rigid plastic that will conveniently provide sufficient rigidity and strength while affording limited flexibility to accommodate expansion and contraction of the adjacent concrete slabs. in use, when a concrete slab is. being poured and only contraction crack control is desired, the upper section it) is cut to an appropriate length and positioned in the fresh concrete usually just before or after tamping. The slab may be scored along the edges thereof adjacent the ends of the upper section after is has been positioned. The plastic concrete conforms to the side walls and bottom wall of the upper section 10 and flows around and completely encloses the anchors 22 and 24. Subsequent contraction of the concrete results in the pulling of the wings 22 and 24 and slight deformation of the side walls 15 and 16. The edge 20 produces a stress concentration directly beneath the upper portion to thereby induce the positioning of the contraction crack directly underneath the upper section. Water existing on the top of the concrete slab will tend to follow along the junction between the side walls 15 and 16 and the adjacent concrete; however, the anchors 22 and 24 form effective water blocks to prevent the water from seeping into the contraction crack directly beneath the upper section and possibly causing damage through the effects of expansive-type soils.

When pouring the concrete slab in an environment such as a swimming pool deck, it is appropriate to not I only use contractual crack control, but at least periodically, provide expansion control as well. The operator, when desiring to provide such expansion control, mounts the lower section 12 to the upper section 10 by simply forcing the two together causing the side walls 34 and 36 of the lower i2 to bow slightly outwardly as the flanges 40 and 32 follow the contour of the V- shaped bottom 18 of the upper section it). As the flanges 40 and 42 slide upwardly along the bottom 18 to subsequently snap into the channels 30 and 32, they provide a unitary structure having a total depth from the top wall 14 to the bottom wall 38., of approximately the same depth as the concrete slab. The unitary structure comprising the upperand lower sections, may appropriately'be positioned by any well known technique such as prestaking and then concrete is poured against 

1. A concrete expansion/contraction joint comprising: a. an elongated upper section having a top wall and two side walls depending from said top wall; b. a pair of water blocking anchors each extending outwardly from a side wall and longitudinally along said side wall; means forming longitudinally extending channels in each of said side walls beneath said water blocking anchors; c. a bottom joining said side walls, said bottom including means for inducing a contractual crack; and d. an elongated lower section having two side walls, a bottom wall and an open top; a pair of longitudinally extending inwardly directed locking flanges positioned adjacent said open top, engaging said longitudinally extending channels to lock said upper and lower sections together and enclosing said contractual crack inducing means to form a unitary structure; said upper and lower sections when embedded in concrete being inseparable.
 2. The combination as set forth in claim 1 wherein said contractual crack inducing means is a longitudinally extending edge formed as part of a V-shaped bottom of said upper section.
 3. The combination as set forth in claim 1 wherein said upper and lower sections each include longitudinally extending trough shaped internal webs extending from one side wall to the other to permit said joint to be compressed. 